Django 保存点回滚捕获完整性错误会导致 TransactionManagementError答案

【问题标题】：Django savepoint rollback on catching an Integrity Error causes a TransactionManagementErrorDjango 保存点回滚捕获完整性错误会导致 TransactionManagementError
【发布时间】：2016-11-18 07:57:31
【问题描述】：

我在 Django 的 transaction.atomic 块中运行以下代码。

@transaction.atomic()
def test():
   a.save()
   sid = transaction.savepoint()
   try:
       b.save()
       transaction.savepoint_commit(sid)
   except IntegrityError as e:
       transaction.savepoint_rollback(sid)
   c.save()

这段代码给了我以下错误-

TransactionManagementError
An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.

我点击了官方文档中的以下链接。 https://docs.djangoproject.com/en/1.10/topics/db/transactions/#s-savepoint-rollback

我在这里错过了什么？

编辑：- 添加堆栈跟踪。

    File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/models/manager.py", line 122, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/models/query.py", line 401, in create
    obj.save(force_insert=True, using=self.db)
  File "/Users/vibhor/Documents/juggernaut/user-persistence-service/books/models/books.py", line 243, in save
    transaction.savepoint_rollback(sid)
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/transaction.py", line 66, in savepoint_rollback
    get_connection(using).savepoint_rollback(sid)
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/backends/base/base.py", line 328, in savepoint_rollback
    self._savepoint_rollback(sid)
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/backends/base/base.py", line 288, in _savepoint_rollback
    cursor.execute(self.ops.savepoint_rollback_sql(sid))
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/backends/utils.py", line 59, in execute
    self.db.validate_no_broken_transaction()
  File "/Users/vibhor/Documents/juggernaut/user-venv-new/lib/python2.7/site-packages/django/db/backends/base/base.py", line 429, in validate_no_broken_transaction
    "An error occurred in the current transaction. You can't "
TransactionManagementError: An error occurred in the current transaction. You can't execute queries until the end of the 'atomic' block.

【问题讨论】：

请将完整的错误回溯添加到您的帖子中！这样我们就可以看到是哪个命令导致了问题。

标签： python django postgresql django-models transactions

【解决方案1】：

我认为您遇到了文档中描述的这个问题：

保存点可用于通过执行部分回滚从数据库错误中恢复。如果您在atomic() 块内执行此操作，则整个块仍将回滚，因为它不知道您已经处理了较低级别的情况！为了防止这种情况，您可以使用以下函数控制回滚行为...

如那里所述，您可能想要执行transaction.set_rollback(False) 以防止整个原子块被回滚。

现在，您手动执行此操作是否有原因？您发布的代码可以使用嵌套的原子块完成同样的事情，并且如文档所述：

当 atomic() 装饰器嵌套时，它会创建一个保存点以允许部分提交或回滚。强烈建议您使用 atomic() 而不是下面描述的函数。

【讨论】：

【解决方案2】：

如documentation 中所述：

为了保证原子性，atomic 禁用了一些 API。尝试在原子块内提交、回滚或更改数据库连接的自动提交状态将引发异常。

实现你想要的正确方法是创建另一个atomic 块：

@transaction.atomic()
def test():
   a.save()
   try:
       with transaction.atomic():
           b.save()
   except IntegrityError:
       #handle exception here...
       ...
   c.save()

【讨论】：

【解决方案3】：

@transaction.atomic()
def test():
   a.save()
   sid = transaction.savepoint()
   try:
       with transaction.atomic():
           b.save()
           transaction.savepoint_commit(sid)
   except IntegrityError as e:
       transaction.savepoint_rollback(sid)
   c.save()

请检查一下

【讨论】：